Derating Sub Panel For Solar

This panel had to be upgraded due to the large 13kw ground mount solar pv system being installed.

Derating sub panel for solar.

On this project i was hired as a sub contractor to install the electrical panel for a larger well known solar company. The pvwatts default overall dc to ac derate factors are based on a system with a string inverter. Pvwatts applies derate factors to determine the amount of ac power that will flow into the grid from the solar array accounting for many of the environmental characteristics of the site as well as system design and chosen components. The photovoltaic pv derating factor is a scaling factor that homer applies to the pv array power output to account for reduced output in real world operating conditions compared to the conditions under which the pv panel was rated.

Design shows main breaker to be derated to 150a in order to stay below 120 of bus rating 150 70 220a 240a. John smith is a homeowner in california looking to reduce his electric bill by going solar and he decided to call an installation company that he found on the internet. The result is that you can shave off a few extra amps before you connect the sub panel output to the main panel board. For example picture a 200a main breaker box feeding a 125a sub panel through a 100a breaker with a 100a main breaker in the 125a sub panel.

A new solar pv system to be installed. Main panel has 200a bus and breaker. An sma sunny boy 2500hf and an sma sunny boy 5000. Pv backfed breaker to be 70a for load side connection to bus.

Consider that we are using two string inverters. This was the first time i ever replaced a electrical panel directly next to a window. Use the derating factor to account for such factors as soiling of the panels wiring losses shading snow cover aging and so on.